• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.99-112
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• 2019

A quantum light source is an essential element for quantum information technology, including quantum communication, quantum sensor, and quantum computer. Quantum light sources including photon number state, entangled state, and squeezed state can be divided into two types according to the generation mechanism, namely single emitter and non-linear based systems. The single emitter platform contains atom/ion trap, solid-state defect/color center, two-dimensional material, and semiconductor quantum dot, which can emit deterministic photons. The non-linear based platform contains spontaneous parametric down-conversion and spontaneous four-wave mixing, which can emit probabilistic photon pairs. For each platform, we give an overview of the recent research trends of the generation, manipulation, and integration of single photon and entangled photon sources. The characteristics of quantum light sources are investigated for each platform. In addition, we briefly introduce quantum sensing, quantum communication, and quantum computing applications based on quantum light sources. We discuss the challenges and prospects of quantum light sources for quantum information technology.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.1
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• pp.1-9
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• 2006

We introduce our in-house program, NANOCAD, for the modeling and simulation of carrier transport in nanoscale MOSFET devices including quantum-mechanical effects, which implements two kinds of modeling approaches: the top-down approach based on the macroscopic quantum correction model and the bottom-up approach based on the microscopic non-equilibrium Green’s function formalism. We briefly review these two approaches and show their applications to the nanoscale bulk MOSFET device and silicon nanowire transistor, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.92-92
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• 2010

Replacing the existing illumination with solid-state lighting devices, such as light-emitting diodes (LEDs) are expected to reduce energy consumption and environmental pollution as they provide better efficiency and longer lifetimes. Currently, white light emitting diodes are composed of UV or blue LED with down-converting materials such as highly luminescent phosphors White light-emitting diodes (LED) were fabricated with multi-shell nanocrystal quantum dots for enhanced luminance and improved stability over time. Multi-shell quantum dots (QDs) were synthesized through one pot process by using the Successive Ionic Layer Adsorption and Reaction (SILAR) method. As prepared, the multi-shell QD has cubic lattice of zinc-blend structure with semi-spherical shape with quantum yield of higher than 60 % in solution. Further, highly fluorescent multi-shell QD was deposited on the blue LED, which resulted in QD-based white LED with high luminance with excellent color rendering properties.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1674-1688
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• 2023

The remarkable advancement of quantum steganography offers enhanced security for quantum communications. However, there is a significant concern regarding the potential misuse of this technology. Moreover, the current research on identifying malicious quantum steganography is insufficient. To address this gap in steganalysis research, this paper proposes a specialized quantum steganalysis algorithm. This algorithm utilizes quantum machine learning techniques to detect steganography in general quantum secure communication schemes that are based on pure states. The algorithm presented in this paper consists of two main steps: data preprocessing and automatic discrimination. The data preprocessing step involves extracting and amplifying abnormal signals, followed by the automatic detection of suspicious quantum carriers through training on steganographic and non-steganographic data. The numerical results demonstrate that a larger disparity between the probability distributions of steganographic and non-steganographic data leads to a higher steganographic detection indicator, making the presence of steganography easier to detect. By selecting an appropriate threshold value, the steganography detection rate can exceed 90%.

• Journal of Powder Materials
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• v.29 no.6
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• pp.453-458
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• 2022

We successfully synthesize water-dispersible CTAB-capped CdSe@ZnS quantum dots with the crystal size of the CdSe quantum dots controlled from green to orange colors. The quenching effect of Fe(DTC)₃ is very efficient to turn off the emission light of quantum dots at four molar ratios of the CdSe quantum dots, that is, the effective covering the surface of quantum dots with Fe(DTC)₃. However, the reaction with Fe(DTC)₃ for more than 24 h is required to completely realize the quenching effect. The highly quenched quantum dots efficiently detect nitric oxide at nano-molar concentration of 110nM of NO with 34% of recovery of emission light intensity. We suggest that Fe(DTC)₃-hybridized CdSe@ZnS quantum dots are an excellent fluorescence resonance energy transfer probe for the detection of nitric oxide in biological systems.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.103-106
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• 2003

The microscopic quantum Langevin equations for two-level atom electric dipole systems are derived. starting from the microscopic interaction Hamiltonian of the systems. By averaging those microscopic equations over a macroscopic region, the macroscopic quantum Langevin equations are derived and the effect of local-field corrections on the two-level systems is investigated.

• Journal of Information Processing Systems
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• v.17 no.1
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• pp.151-162
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• 2021

Quantum information has passed the theoretical research period and has entered the realization step for its application to the information and communications technology (ICT) sector. Currently, quantum information has the advantage of being safer and faster than conventional digital computers. Thus, a lot of research is being done. The amount of big data that one needs to deal with is expected to grow exponentially. It is also a new business model that can change the landscape of the existing computing. Just as the IT sector has faced many challenges in the past, we need to be prepared for change brought about by Quantum. We would like to look at studies on quantum communication, quantum sensing, and quantum computing based on quantum information and see the technology levels of each country and company. Based on this, we present the vision and challenge for quantum information in the future. Our work is significant since the time for first-time study challengers is reduced by discussing the fundamentals of quantum information and summarizing the current situation.

• Journal of the Korean Mathematical Society
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• v.45 no.4
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• pp.1075-1087
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• 2008

We study a class of KMS-symmetric quantum Markovian semigroups on a quantum spin system ($\mathcal{A},{\tau},{\omega}$), where $\mathcal{A}$ is a quasi-local algebra, $\tau$ is a strongly continuous one parameter group of *-automorphisms of $\mathcal{A}$ and $\omega$ is a Gibbs state on $\mathcal{A}$. The semigroups can be considered as the extension of semi groups on the nontrivial abelian subalgebra. Let $\mathcal{H}$ be a Hilbert space corresponding to the GNS representation con structed from $\omega$. Using the general construction method of Dirichlet form developed in [8], we construct the symmetric Markovian semigroup $\{T_t\}{_t_\geq_0}$ on $\mathcal{H}$. The semigroup $\{T_t\}{_t_\geq_0}$ acts separately on two subspaces $\mathcal{H}_d$ and $\mathcal{H}_{od}$ of $\mathcal{H}$, where $\mathcal{H}_d$ is the diagonal subspace and $\mathcal{H}_{od}$ is the off-diagonal subspace, $\mathcal{H}=\mathcal{H}_d\;{\bigoplus}\;\mathcal{H}_{od}$. The restriction of the semigroup $\{T_t\}{_t_\geq_0}$ on $\mathcal{H}_d$ is Glauber dynamics, and for any ${\eta}{\in}\mathcal{H}_{od}$, $T_t{\eta}$, decays to zero exponentially fast as t approaches to the infinity.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.4
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• pp.527-531
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• 2012

In this paper, a novel DPSO-QI (Distributed PSO with quantum-infusion mechanism) algorithm improving one of the fatal defect, the so-called premature convergence, that degrades the performance of the conventional PSO algorithms is proposed. The proposed scheme has the following two distinguished features. First, a concept of neighborhood of each particle is introduced, which divides the whole swarm into several small groups with an appropriate size. Such a strategy restricts the information exchange between particles to be done only in each small group. It thus results in the improvement of particles' diversity and further minimization of a probability of occurring the premature convergence phenomena. Second, a quantum-infusion (QI) mechanism based on the quantum mechanics is introduced to generate a meaningful offspring in each small group. This offspring in our PSO mechanism improves the ability to explore a wider area precisely compared to the conventional one, so that the degree of precision of the algorithm is improved. Finally, some numerical results are compared with those of the conventional researches, which clearly demonstrates the effectiveness and reliability of the proposed DPSO-QI algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.564-582
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• 2015

This paper proposes a novel swarm intelligence optimization method which integrates bacterial foraging optimization (BFO) with quantum computing, called quantum bacterial foraging optimization (QBFO) algorithm. In QBFO, a multi-qubit which can represent a linear superposition of states in search space probabilistically is used to represent a bacterium, so that the quantum bacteria representation has a better characteristic of population diversity. A quantum rotation gate is designed to simulate the chemotactic step for the sake of driving the bacteria toward better solutions. Several tests are conducted based on benchmark functions including multi-peak function to evaluate optimization performance of the proposed algorithm. Numerical results show that the proposed QBFO has more powerful properties in terms of convergence rate, stability and the ability of searching for the global optimal solution than the original BFO and quantum genetic algorithm. Furthermore, we examine the employment of our proposed QBFO for cognitive radio spectrum allocation. The results indicate that the proposed QBFO based spectrum allocation scheme achieves high efficiency of spectrum usage and improves the transmission performance of secondary users, as compared to color sensitive graph coloring algorithm and quantum genetic algorithm.